1. Field of the Invention
The invention relates to a system, method, apparatus, and computer program product for avoiding aircraft collisions and more particularly to a system, method and apparatus for avoiding collision with stationary obstacles.
2. Description of Related Art
Aircraft safety is principally a matter of preventing collisions with other aircraft, obstructions and the ground. Air traffic control is provided in virtually all modern airports and is the product of the National Air Space System (NAS) in the United. States. Such control involves many elements including air-to-ground communications and both airborne and ground mounted electronic equipment. Air navigation also entails airborne and ground mounted electronic equipment and systems. Examples of such systems currently in use include: omni-directional radio range (VOR) stations, VORTAC or VOC/DME stations, doppler radar, inertial navigation systems, Loran C, Omega, NAVSTAR GPS, microwave landing systems (MLS), non-directional beacons (NDB), radar, and tactical air navigation (TACAN). While NAVSTARGPS is widely utilized by surface craft for marine navigation, and is in use by the U.S. military, it has not to date been adapted to commercial aircraft use. The aforelisted aircraft navigation systems may be used in conjunction with a flight management computer system (FMCS) which combines the capabilities of a navigation computer and those of an aircraft performance computer. The FMCS may perform only the area navigation function, but is more likely to utilize inputs from several sensors when they are installed and available, such as VOR/DME, Loran C, Omega/VLF, TACAN and an inertial reference system. Unless the pilot manually selects a specific navigation aid to be used (such as VOR/DME), the computer conventionally will follow a selection hierarchy, with cross-checks to other aids. In the event that no reliable external navigation aid is available, the navigation computer will go into an inertial navigation mode.
Aircraft collision avoidance systems are generally independent of ground-based systems and are intended to allow the pilot of an aircraft to observe and avoid other aircraft, regardless of weather. In civil aviation aircraft are presently kept separated by the use of communication, navigation, and a surveillance system based on the ground. The earliest type of airborne equipment comprised airborne radar. However, it soon became apparent that at the radio frequencies low enough to penetrate heavy rain (below about 10 GHz), the antenna size would have to be prohibitively large in order to resolve the angular difference between a collision course (no change of bearing) and a potentially passing course (small change of bearing). In the early 1960's so-called black boxes were provided on aircraft to provide warning based on the distance between aircraft and their rate of closure.
Since the mid-1970's efforts have concentrated on the use of hardware already carried by most aircraft, namely, the transponder of the air-traffic control radar beacon system (ATCRBS). These transponders reply to interrogations from secondary surveillance radars (SSRs) on the ground. For an independent collision avoidance system, it was proposed to interrogate these transponders from the air (in addition to continuing to reply to interrogations from the surveillance radar). This system is known as the traffic alert and collision avoidance system (TCAS). In a TCAS equipped aircraft, replies are fed to a computer which generates two types of information: (1) traffic advisories that tell the pilot there are nearby aircraft of known distance, altitude and approximate bearing; and (2) resolution advisories that advise immediate evasive action (for example, "climb" or "descend"). These are displayed to the pilot by various means, depending on customer preference, and have included synthetic voice, modification of the weather radar display, and modification of the vertical speed indicator.
The Problems
While the foregoing systems provide reasonable safety when used for their intended purposes, none of these systems effectively avoid crashes into mountainous terrain or ground hazards where the pilots are lost or mistaken as to their present position. This is particularly true in attempting landing at airports proximate to such hazards with which the pilots are unfamiliar. An example is a recent incident where a commercial civil aircraft turned into a mountain in South America. There is thus a need for providing an improved system, method and apparatus for avoiding aircraft collision with stationary ground hazards.
Commercial aircraft developed during the 1980s used digital electronics usually embodied in an integrated flight management system (FMS). Such a system includes automatic flight control, electronic flight instrument displays, communications, navigation, guidance, performance management, and crew alerting to improve safety, performance and economics. In order for a pilot to effectively fulfill the role of flight manager he/she must have ready access to relevant flight information and suitable means to accomplish aircraft control within reasonable workload bounds. The extensive data-processing capabilities and integrated design of a flight management system provide the pilot with access to pertinent information and a range of control options for all flight phases. The basic elements of such an integrated flight management system are shown diagrammatically in FIG. 1.
Referring to that figure the avionics may be subdivided into three basic groups: sensors, computer subsystems and cockpit controls/displays. FIG. 1 shows the intrasystem communication data buses diagrammatically at 10. The cockpit control operate the sensors and computer subsystems, and the displays are supplied with raw and processed data from them. Illustrative radio sensors are shown at 12, air data computers at 14, flight management computers (FMC) at 16, caution and warning computers at 18, and flight control computers at 20. The FMC computers provide input to a control display unit 22 while the caution and warning system provides input to a caution and warning display 24. Electronic attitude director indicator (EADI) is shown at 26 and an electronic horizontal situation indicator (EHSI) is shown at 28. The electronic horizontal situation indicator may include map and weather radar (WXR) displays. Other displays such as the mach/airspeed indicator (M/ASI), radio directional magnetic indicator (RDMI), instantaneous vertical speed indicator (IVSI), and thrust indicator are indicated generally at 30. The inertial reference unit is indicated at 32, while the communication systems, such as VHF, HF, and air traffic control, are indicated at 34. Control panels are shown generally at 36 providing control of such systems as the electronic flight instrument system (EFIS), inertial reference system (IRS), instrument landing system (ILS), navigation, communication, and weather radar (WXR) systems. A control system electronic unit is shown at 38 and an autopilot is shown at 40.
The electronic attitude director indicator (EADI) provides a cathode ray tube display of information including attitude information showing the aircraft's position in relation to the instrument landing system or a VHF omnirange station. In addition, the EADI indicates the mode in which the automatic flight control system is operating and presents the readout from the radio altimeter. Ground speed is displayed digitally at all times near the air speed indicator.
The electronic horizontal situation indicator (EHSI) provides an integrated multicolor map display of the aircraft's position, plus a color weather radar display. Wind direction and velocity for the aircraft's present position and attitude, provided by the inertial reference system, are shown at all times. Both the horizontal situation of the airplane and its deviation from the planned vertical path are also provided, thus making it a multidimensional situation indicator. The EHSI operates in three primary modes, namely, as a map display, a full compass display, and a VOR mode that displays a full or partial compass rows. The map displays are configured to present basic flight plan data, including such parameters as the route of flight, planned weight points, departure or arrival runways, and tuned navigational aids. Predictive information is also displayed. Thus, the EHSI may provide a display of a prediction of the path over the ground on the basis of current ground speed and lateral acceleration. A second prediction may be an attitude range arc used for climb or descent to show where the aircraft will be when the target altitude is reached. This feature allows the pilot to quickly assess whether or not a target altitude will be reached before a particular location over the ground.
The essential display elements of a typical alerting system for aircraft is a cathode ray tube with a multicolor capability located at a point easily viewable from a pilot's position such as on the pilot's forward main engine instrument panel. Two colors are generally used, one for warnings (emergency operational or aircraft system conditions that require immediate corrective or compensatory action by the crew) which may be presented in red alphanumerics; cautions, conditions that require immediate crew awareness and eventual corrective or compensatory action and advisories may be presented with amber alphanumerics.
Military aircraft have instrumentation requirements which include essentially the instrumentation described above in addition to instrumentation for the performance of special mission needs. The latter category of displays include a head-up display in the forward field of view and a radar map display, presenting radar reflections of ground imagery and targeting information. The control panel display may include a moving map, i.e. an electronic map of the area moving below the aircraft.